Free Energy Contribution to Gas Chromatographic Separation of Petroselinate and Oleate Esters

Abstract

The ease of separation by gas chromatography between petroselinic and oleic acids depends on the alcohol moieties of their esters. The esters of higher molecular weight alcohols tend to be better separated on a 90%-biscyanopropyl-10%-cyanopropylphenyl polysiloxane capillary column (30 m × 0.25 mm i.d.). By analysis of free energies contribution from different parts of the molecules, it is tentatively concluded that the interaction between the double bond and the column stationary phase is interfered by the bulky alkyl group, and it is the major driving force for the separation of the two fatty acids.

Gas Chromatographic Separation and Identification of Jacaric and Punicic 2‐Ethyl‐1‐Hexyl Esters

“…Acceptable resolution (R s = 1.01) of the JA and PA 2-ethyl-1-hexyl esters was obtained. The results agreed with the reports of Isbell et al [11] and Sansa-ard et al [12] on the separations of petroselinate and oleate esters. Generally, baseline separation (R s ≥1.5 or 6σ) is ideal for accurate quantitative analysis.…”

“…The g sln G u of JA and PA alkyl esters were calculated according to Sansa-ard et al [12] as shown in Eqs. (4) and (5), respectively.…”

“…To clarify the effects of alkyl esters on the separation of CLN isomers, Gibbs energy of transfer from solution to gas of the double bond (� g sln G u ) proposed by Sansa-ard et al [12] was evaluated. The Microsoft Excel worksheet for the calculation of the standard Gibbs energies of transfer from solution to gas of saturated fatty acid ( g sln G 0 18:0 ) and the unsaturated fatty acid (� g sln G 0 18:3 (JA) and � g sln G 0 18:3 (PA) ) and the differences in g sln G u at 230 °C is demonstrated and available in the supplemental data file.…”

“…The pair of petroselinic (c6-18:1) and oleic (c9-18:1) acids is an example. The two isomers could not be separated as the methyl ester derivatives but they were well resolved as the phenylethyl [9], isopropyl [10] and longer alkyl esters [11,12]. Similarly, separations of the four conjugated linoleic acid (CLA) isomers on a 50-m cyanopropyl polysiloxane column were improved when Abstract The present study demonstrates the separation of a critical pair of conjugated linolenic acid (CLN) isomersjacaric acid (JA; c8, t10, c12-18:3) and punicic acid (PA; c9, t11, c13-18:3)-on a 60-m conventional Supelcowax 10 column.…”

An Empirical Equation for Estimation of Kinematic Viscosity of Fatty Acid Methyl Esters and Biodiesel

“…Thus, the difference between the free energies of viscous flow (n d ΔG db ) of an unsaturated FAME (ΔG unsat ) and a saturated FAME (ΔG sat ) is shown in Eq. 19 [21]. or where db and n d stand for the double bond and the number of double bonds, respectively.…”